1. Field of the Invention
The present invention generally relates to data transmission and reception, and more particularly to a method for transmitting data periodically transmitted and data transmitted in response to the occurrence of an event.
2. Description of the Related Art
Methods for determining a packet loss in periodical packets which are periodically and continuously transmitted include confirming a sequence number assigned to the packet. A receiving apparatus can detect the packet loss by finding that the sequence number is missing.
On the other hand, Japanese Patent Application Laid-Open No. 2005-328131 discusses a method for determining a packet loss in an event packet transmitted in response to the occurrence of an event. In Japanese Patent Application Laid-Open No. 2005-328131, a transmission apparatus adds different marker bits to a head packet and a tail packet respectively in a packet group relating to a telop which is non-periodically transmitted. A receiving apparatus determines, when it does not receive the tail packet within a predetermined period of time elapsed since it received the head packet, that the tail packet is lost.
However, it may take time until a loss in event data is detected depending on the event data.
As an example of such a case, the number of packets belonging to a packet group in event data varies. If the number of packets belonging to a packet group in event data varies, an actual period of time and a predicted period of time elapsed since a head packet was received until a tail packet is received differ from each other. Particularly when the number of packets in the packet group becomes smaller than that in a packet group in event data so far received, the predicted period of time elapsed since the head packet was received until the tail packet is received becomes longer than the actual period of time. If the packet is waited for until the predicted period of time elapses, it takes time until a loss in the tail packet is detected. When the number of packets in the event data differs depending on an event, therefore, it may take time until a loss in the event data is detected.
If the number of packets in the event data is only one, different marker bits cannot be added to a head packet and a tail packet, respectively. Accordingly, a packet loss in the event data cannot be detected until the succeeding event data is received, for example.